1. Field of the Invention
The present invention relates to the field of design and construction of bicycle frames. More particularly, the present invention relates to the field of design and construction of the front suspension forks for bicycles.
2. Description of the Prior Art
A typical bicycle front fork includes the following main components: a steering tube, a crown, and two front legs. The steering tube is connected to the handlebar. The crown interconnects the steering tube and the two legs.
Many bicycle fork legs now utilize various suspension systems. Commonly a suspension leg utilizes a telescoping assembly which includes an upper tube and a lower tube. The upper and lower tubes are slidably engaged with damping devices to form a suspension leg.
In bicycles utilizing wheel rim brakes, a brake arch is often attached between the two fork legs. The brake arch is typically a reversed U-shaped member having a bent top section and two straight lower sections integrally connected to opposite ends of the bent top section.
The brake arch serves several functions. First, the bent top section often carries a brake cable stop, and the two straight lower sections each carry a brake post; thereby serving as an integral part of the bicycle wheel rim brake mechanism. Second, it resists torsional and side loading forces exerted on the front legs, thereby preventing the twisting, rotating and separate movement of the legs. Third, it transmits and re-distributes the tension among the two legs, thereby helping the alignment and balance of the entire front fork.
In the prior art, the most common method of attaching the brake arch to the fork legs is by threaded fasteners. This type of attachment can be seen in U.S. Pat. Nos. 4,971,344 and 5,186,481 issued to Turner, U.S. Pat. No. 5,238,259 issued to Wilson et al., U.S. Pat. No. 5,284,352 issued to Chen, and U.S. Pat. No. 5,398,954 issued to Chonan.
A second prior art method of attaching the brake arch to the fork legs appears to be welding. As shown in U.S. Pat. No. Des. 340,434, the brake arch may be welded to the exterior sidewalls of the fork legs.
A third possible method of attaching the brake arch to the fork legs may be by press-fitting. According to this method, the bottom ends of the brake arch would have respective bracing members. The bracing member could be press-fitted with a portion of a fork leg.
The disadvantage of the press-fitting method is that it requires high-tolerance machining of both the brake arch and the fork legs to ensure high-precision alignment and orientation of the brake arch and the fork legs. Typically, high-precision press-fitting attachment requires a high-tolerance of less than .+-.0.003 inch. This requirement makes the machining of the brake arch and fork legs a yery difficult and expensive task.
It is desirable to have a new method of producing a brake arch and fork legs assembly.